Suitability of Wild Oat (Avena fatua), False Cleavers (Galium spurium), and Volunteer Canola (Brassica napus) for Harvest Weed Seed Control in Western Canada

As herbicide resistance increases, new non-chemical methods of managing weeds are needed. Harvest weed seed control (HWSC) is a new method of managing weeds that targets weeds normally spread by combine harvesters to prevent them from getting into the soil seedbank and being a problem in future years. A study was conducted to determine if 3 problematic Canadian weeds (wild oat, false cleavers, and volunteer canola) still had enough seed on the plant at the time of crop harvest, at a height where the seeds would go through the combine, for HWSC to be a potential method of weed control for western Canada. Wild oat consistently dropped seeds early with only 56% of seeds left at swath timing and down to about 30% by combine harvest. Most of the seeds are produced high enough to be easily collected by the combine. Cleavers seed retention was different based on location and year it was measured, but generally fewer seeds were shed compared to wild oat. The majority of seed would be high enough above the ground for the combine to collect it. Volunteer canola lost very few seeds before combining (~5%) and was also produced high enough above the ground for the combine to collect it. Out of the three species we looked at, volunteer canola made the best target followed by cleavers and finally wild oat. This study showed that HWSC methods may work in western Canada, but how well will depend on what species is being targeted and the location and year specific environment conditions.